Heat treatment furnaces



June 27, 1967 w, BECKER 3,328,015

' HEAT TREATMENT FURNACES Filed April 21, 1964 5 Sheets-Sheet 1Jnrenfon- June 27, 1967 Filed April 21, 1964 w. BECKER HEAT TREATMENTFURNACES 5 Sheets-Sheet 2 June27, 1967 v w. BECKER I 3,328,015.

' HEAT TREATMENT FURNACES Filed April 21, 1964 5 Sheets-Sheet 5Wren/or.-

United States Patent 10 Claims. (c1. 2665) This invention relates tocontinuous furnaces for the heat treatment of rolled stock which hasbeen wound into coils, for example for the bright annealing of coils ofsteel strip. For a variety of purposes, rolled stock in wire and stripform must have a com letely uniform material structure over its wholelength, and it is difficult to achieve this with the conventionaldevices in the heat treatment given to normalize or structurally convertcoils of rolled stock. The difficulties increase in proportion to thesize of the coils. It is technically impossible to heat treat coils ofmore than 2 metres diameter in the pot of a pot type annealing furnace,and it is economically unsatisfactory to anneal such large coils belowthe hood. When coils are annealed in continuous furnaces having astationary or moving hearth, uniform and thorough heating of the coilsis delayed or prevented by disturbances in the heat supply at the placesof contact with the hearth, while in continuous furnaces in which thecoils pass through the treatment chamber freely suspended below acarrier bar, the places, which are admittedly smaller, where the coilscontact the hangers similarly delay uniform and thorough heating. Thereis the particular disadvantage in this latter kind of furnace that thetemperature in the bottom part of the heat treatment chamber is lower,possibly considerably lower, than in the top part, so that complexdevices must be provided to circulate the atmosphere of the heattreatment chamber and, if the heat treatment is performed in aprotective gas, these devices represent a very high constructional andoperational outlay. It is an object of the invention to provide acontinuous furnace for the heat treatment of rolled stock which has beenwound up to form coils, for example for bright annealing strip steelcoils or the like, which, with a relatively low outlay, especially arelatively low operational outlay, ensure substantially uniform heattreatment of the rolled stock by heating and recooling.

To this end, according to this invention, such a furnace comprises anumber of heat treatment stations and a conveyor for conveying the coilsstep by step from one station to the next, the conveyor comprising aconveyor beam, at least one carriage which is movable along the beam anda hub which is arranged to pass through and support a coil and isrotatably suspended from the carriage at each end, and each stationhaving at least one driving shaft which extends from the furnace walland is axially movable to enable it to be introduced into the hub torotate the hub and thus to rotate the coil at the station.

In this furnace the coils can be rotated in the treatment chamber duringthe treatment stage which is critical for the final structure so thatdespite a stationary or sluggishly moving furnace atmosphere and despitetemperatures being different at different levels in the treatmentchamber, the coils are heated and recooled very uniformly without beingborne for any prolonged length of time at the same places where the heatsupply may be impaired.

Preferably, the hub is suspended from the carriage at each end by a loopor belt and the beam is movable upwards and downwards, downward movementafter the shaft has been introduced into the hub transferring the loadof the hub and coil to the shaft and releasing the 'ice hub from theloops or belts to enable the hub to be rotated.

Preferably also there are two coaxial shafts at each station, one ofwhich is introduced into each end of the hub.

For reliable guiding of the coils on the hubs and to locate the hubswithin the loops, the hubs have flanges between which the coils arereceived and the loops which engage around the hubs outside the flangesare interconnected at their bottoms, e.g., by turnbuckles. The loops maybe moved along the conveyor beam which is preferably an I beam bycarriages which run along the bottom flange. To move the carriages theymay have sets of teeth which engage in the bottom runs of endless drivenchains; the bottom runs extending on each side of the web between thecarriage and the top flange of the beam. This arrangement of the bottomruns of the chains provides a reliable connection of the carriages tothe chain independently of the actual height of the beam so that nospecial means are required to couple the carriages with the chain. Also,since the chains reverse upwards before and after the furnace treatmentchamber, it is a very simple matter to couple and uncouple the carriagesto and from the chain before and after treatment.

To ensure good heat economy and to inhibit unwanted heat exchangebetween adjacent treatment stations operating at different temperaturesfrom one another, the stations are adapted to be closed off from oneanother and from the outside by externally operated doors. Conveniently,special door chambers forming locks are disposed between consecutivetreatment stations and before and after the end stations, the chambersbeing adapted to be closed off from each adjacent station and from theoutside by externally operated doors. Consequently, each treatmentstation has a reliable closure in each direction in the form of twodoors with an air space therebetween. To inhibit the entry ofatmospheric air into the furnace chamber when the furnace is beingoperated with an inert gas, an entry lock and an exit lock are provided.For very rapid and uniform heating of the coils, the heat treatmentstations comprise electric or gas heating elements which supply heatdirectly to the side surfaces of the coils.

A preheating station may precede the heat treatment station, to shortenthe warming-up time, and the heat treatment station is followed by aheat-exchange station providing a controlled cooling of the heat-treatedmaterial from the heat-treatment temperature. To this end, the heatexchange station comprises, laterally adjacent the coils, heat-exchangeducts through which the protective gas preheated in the preheatingstation is conveyed and is returned to the preheating station.

An example of a continuous furnace constructed in accordance with theinvention is illustrated in the accompanying drawings in which:

FIGURE 1 is a side view of the suspended coil;

FIGURE 2 is a vertical cross-section of the coil shown in FIGURE 1;

FIGURE 3 is a section similar to FIGURE 2, but showing the partsdifferently disposed;

FIGURE 4 is a side view similar to FIGURE 1, but showing the partsdifferently disposed;

FIGURE 5 is a side view of parts of the furnace adjacent those shown inFIGURE 1;

FIGURE 6 is a view similar to FIGURE 5 but showing the part differentlydisposed;

FIGURE 7 is a section similar to FIGURE 2, but showing a different partof the furnace;

FIGURE 8 is a section similar to FIGURE 5, but showing yet another partof the furnace;

FIGURE 9 is a side view to a smaller scale of another part of thefurnace;

FIGURE 10 is a side view similar to FIGURE 9, but showing another partof the furnace;

FIGURE 11 is a vertical section of the part of the furnace shown inFIGURE 10;

FIGURE 12 is a section through yet another part of the furnace;

FIGURE 13 is a side view showing another detail of the furnace; and,

FIGURE 14 is a side view showing another detail.

Referring to FIGURES 1 and 2, a coil A of steel strip is supported byits inner periphery on a bush B between flanges D. The bush B issuspended in two wire loops C which engage around the bush outside theflanges D and are interconnected at their bottoms by a turnbuckle E. Theloops C are suspended through a carrier framework F from a carriage G.The carriage G has four rollers J running on the bottom flange of anI-beam K. On each side of the web of the beam K, the carriage G engagesthrough a top set of teeth L with the bottom run M of a stepwise drivenroller chain running below the top flange of the beam K. The chain movesa number of carriages of the kind shown in the drawings through thefurnace treatment chamber simultaneously. The furnace chamber issubdivided into a number of consecutive treatment stations andcomprises, in this example which is for bright annealing strip steel, apreheating station, an annealing station, a heat exchange station forthe controlled cooling of the coils from the annealing temperature, andat least one cooling station to cool the coils substantially to ambienttemperature.

As can be seen in FIGURE 2, at the stations for the heat treatment ofthe coils, coaxial driving shafts N are provided which extend throughthe furnace walls and which each have a journal P at their end extendinginto the furnace chamber. The journals P are aligned with the axis ofthe bush B which has entered the treatment station. The shafts N aremoved axially to introduce their journals P into the bushes B.

The beam K is then lowered by a vertical distance H into the positionshown in FIGURE 3. The bush B bearing the coil A then engages with thejournals P and the loops C are disengaged from the bush B so that thebush B can be rotated by the shafts N. The bush B, as it rotates,rotates the coil A on it, so that the coil rotates in the same sense asthe bush B but at a lower speed than the bush.

FIGURES 5 and 6 show the way of suspending the vertically movable beam Kon the furnace frame. The beam K is suspended through the agency oflinks k on one horizontal arm each of bell-crank levers Q mounted on thefurnace frame for pivoting around horizontal axes, the downwardlyextending arms of the levers Q being connected via links q to a thrustrod. The beam K is shown in its top position in FIGURE 5 and in itsbottom position in FIGURE 6.

FIGURE 7, which is a vertical cross-section through the annealingstation, shows as well as the means for suspending and moving the coilsA, bearings O for the shafts N. The bearings are themselves gastight andare a gastight fit in the furnace side walls. The casings of thebearings 0 also receive drives for moving the externally rotated shaftsN in an axial direction. FIGURE 7 also shows heating elements R disposedlaterally adjacent the coil A between the coil and the furnace walls. Inthis case the elements R are gas-heated radiant tubes with bottom gasfeeds and top gas flues.

FIGURE 8 shows a heat exchange station which follows the annealingstation and which provides controlled cooling of the coil from theannealing temperature. For this purpose, heat exchange tubes S aredisposed laterally adjacent the coil A, which in this illustration isborne by the journals P and are disposed between the coil A and thefurnace walls. A cool protective gas is supplied to 4 the tubes Sthrough top ducts U by a blower T which supplies the protective gasheated in the heat exchange station through bottom ducts W and, avoidingthe annealing station, to a preheating station preceding the annealingstation.

FIGURE 9 shows the preheating station which is the first treatmentstation of the furnace and is therefore preceded by an entry lock whichis shown to the left of the preheating station in FIGURE 9 and which hasan outer door a The preheating station chamber, which has provision forrotating the coils introduced into it, is directly supplied with hotinert gas through top delivery apertures in the ducts W extending fromthe heat exchange station. The protective gas, after yielding much ofits heat to the coil A, passes from the preheater chamher through slotsinto the top ducts U and thence, via the heat exchange tubes S, back tothe heat exchange station.

FIGURE 10 shows a cooling station at the end of the furnace followed, asshown on the right in the drawing, by an exit lock having an outer doora If required, a number of cooling stations can be provided dependingupon the amount of cooling required. The cooling station has noprovision for rotating the coils since the coils do not pass throughcritical temperature ranges in the cooling station.

As shown in FIGURE 11, the cooling station has cooling tubes disposed onits side walls and extending to cooling boxes in the top part of thecooling station. Also shown in FIGURES 9 and 10 are the door chambersdisposed between consecutive furnace stations and between each endstation and its lock.

One such door chamber is shown to an enlarged scale and in horizontalsection in FIGURE 12. Each door chamber can be closed off from theadjacent station or lock by an externally operated double door X.

FIGURES 13 and 14 show details of the conveyor chain at the start andend of the furnace. Referring to FIGURE 13, a reversing roller Udisposed in the entry lock (see also FIGURE 9) has a smooth surface onits periphery. Associated with the roller U is a toothed tensioningroller Y which is mounted .at the free end of a single-armed lever andwhich compensates for variations in chain length especially those causedby the lowering and raising of the beam K. Also, the tensioning rollerY, together wit-h the smooth reversing roller U, facilitates theintroduction of the carriages G until their teeth L engage with thebottom chain run M.

Referring to FIGURE 14, in the exit lock the bottom chain run M firstpasses upwards over a smooth guide roller and only then runs over atoothed reversing roller U at a higher level. The bottom run M isdisengaged from the teeth L between the last-mentioned two rollers. Theroller U also serves to drive the chain (see FIG- URE 10).

The vertically movable beam K need extend only through those of thestations which have provision for rotating the coils. In other words,the beams K K in the locks can be fixed in position as can the carrierbeams in the cooling stations. This is why a separation is shown inFIGURE 9 between the vertically movable beam K and the stationary beam Kwhich extends from the preheating station through the entry lock.

The protective gas for the furnace atmosphere is supplied at somesuitable place, such as the centre of the furnace, then flows in bothdirections to the locks. The locks have non-return valves V V throughwhich, after the outer doors a :1 have been closed and after theintermediate doors have been opened, the protective gas entering thelock displaces the atmospheric air which has entered the locks duringthe charging and emptying of the furnace. To ensure that the furnacechamber always remains free from atmospheric air, the furnace includingthe locks should always be operated with the inert gas at a measurablepressure above atmospheric pressure. It is therefore very important forthe outer and inner lock doors to close tightly.

I claim:

1. A continuous furnace for heat treating coils of steel strip and thelike, the furnace comprising a number of heat treatment stations and aconveyor for conveying the coils step by step from one station to thenext, the conveyor comprising a conveyor beam, at least one carriagewhich is movable along the beam and a hub which is arranged to passthrough and support a coil and is suspended from the carriage at eachend, and each station having at least one driving shaft which extendsfrom the furnace wall and is axially movable to enable it to beintroduced into the hub and to rotate the hub upon the disconnectionthereof from the carriage and thus to rotate the coil at the station. 7

2. A furnace according to claim 1, in which the hub is suspended fromthe carriage at each end by a loop or belt and the beam is movableupwards and downwards, downward movement after the shaft has beenintroduced into the hub transferring the load of the hub and coil to theshaft and releasing the hub from the loops or belts to enable the hub tobe rotated.

"3'. A furnace according to claim 2, in which there are two coaxialshafts at each station, one of which is introduced into each end of thehub.

4. A furnace according to claim 2, in which the hub has two flangesbetween which the coil is arranged to fit and the loops or belts supportthe hub outside the flanges and have their bottoms connected together.

5. A furnace according to claim 4, in which the bottoms of the loops orbelts are connected together by a turn-buckle.

6. A furnace according to claim 2, in which the conveyor beam is anI-beam and the carriage runs on the bottom flange of the beam and hastwo sets of teeth which engage in the bottom runs of endless drivingchains which extend one along each side of the web of the beam betweenthe top of the carriage and the top flange of the beam.

7. A furnace according to claim 1, in which the treatment stations areseparated from each other and are closed at the ends of the furnace byexternally operated doors.

8. A furnace according to claim 7, in which there are two doors at eachend of the furnace and between each adjacent pair of stations to formlocks.

'9. A furnace according to claim 1, in which at least one station is aheat treatment station and has electric or gas heating elements forheating the side surfaces of the coils.

10. A furnace according to claim 9, in which a preheating stationprecedes the heat treatment station and a heat exchange station followsthe heat treatment station and a blower is provided for circulatingprotective gas through ducts between heat exchange tubes at the heatexchange station and the chamber of the preheating station.

References Cited UNITED STATES PATENTS 2,254,525 9/1941 Hathaway et al.266-5 X 2,479,102 8/ 1949 Bailey.

2,507,274 5/ 1950 Sevenich.

2,580,283 12/1951' Cone 26 340 X 3,220,891 11/1965 Templeton 148-13 XJOHN F. CAMPBELL, Primary Examiner. I

0 R. F. DROPKIN, Assistant Examiner.

1. A CONTINUOUS FURNACE FOR HEAT TREATING COILS OF STEEL STRIP AND THELIKE, THE FURNACE COMPRISING A NUMBER OF HEAT TREATMENT STATIONS AND ACONVEYOR FOR CONVEYING THE COILS STEP BY STEP FROM ONE STATION TO THENEXT, THE CONVEYOR COMPRISING A CONVEYOR BEAM, AT LEAST ONE CARRIAGEWHICH IS MOVABLE ALONG THE BEAM AND A HUB WHICH IS ARRANGED TO PASSTHROUGH AND SUPPORT A COIL AND IS SUSPENDED FROM THE CARRIAGE AT EACHEND, AND EACH STATION HAVING AT LEAST ONE DRIVING SHAFT WHICH EXTENDSFROM THE FURNACE WALL AND IS AXIALLY MOVABLE TO ENABLE IT TO BEINTRODUCED INTO THE HUB AND TO ROTATE THE HUB UPON THE DISCONNECTIONTHEREOF FROM THE CARRIAGE AND THUS TO ROTATE THE COIL AT THE STATION.